The current asymmetrical digital subscriber line (ADSL) standard is based on discrete multi-tone signalling (DMIT) protocol, wherein each frame is comprised of the IFFT of a number of samples. In ADSL channels, and at such high data rates, it is computationally expensive to fully equalize the channel. Hence, only partial equalization is implemented to constrain the overall effective channel length to a certain number of samples, say v. Then the last v samples of each frame are used as a prefex to the frame, so that in effect the time domain data is chclically convolved with effective overall channel response, composed of the physical channel and the equalizer. FIG. 1 shows the overall situation.
The current equalization technique, which relies on frequency domain 1 ms (least mean square) is computationally expensive, is nonlinear, and its steady state error is light.